In the punch and die art and particularly in the field of high-speed automated forming and punching equipment for punching and forming sheet material, e.g., sheet metal and especially in the case of automated turret punch presses, the punch presses are operated by computer to perform a series of punching or forming operations sequentially. These punch presses which by themselves form no part of the present invention are typically provided with an upper turret and a lower turret that rotate and are indexed intermittently between punching operations. The turrets may, for example, hold as many as a dozen or more separate punches that are used in sequence for performing given operations. When a punch is struck from above by the ram of the punch press, the punch element or punch insert is driven downwardly through the workpiece to perform the punching operation. When released, the punch insert is retracted by a spring provided in the punch assembly. In order to assure a clean separation between the workpiece and the punch insert, a stripper having an opening shaped to conform to the tip of the punch is used to strip the workpiece from the punch tip. The stripper can either be a separate piece or it can be built into the punch guide bushing. When the punch assembly is placed in the punch press, it is important to assure that the tip of the punch is recessed the correct distance within the stripper. In many punching operations it is common for the operator to recess the punch about 0.032 inches within the stripper, i.e., providing a lead of about 0.032 inches.
The present invention described below and shown in the Figures can be applied to a variety of different kinds of punch set types including relatively large diameter punch sets in which the stripper comprises a flat removable circular stripper plate as well as those of a smaller size in which the stripper comprises the lower end of bushing that encloses the punch insert. Although the invention can be applied to punch sets in which stripper and bushing as well as the punch insert are custom made by the manufacturer, it is particularly applicable to stock punch and stripper sets of a relatively small size that are supplied by numerous manufacturers and are available commercially in many standard sizes and configurations. These “stock” or standard size punch sets are usually kept in stock by the end user. To make a complete punch mechanism using a stock punch insert and stripper set, the manufacturer provides the punch head and spring assembly to which the user attaches his punch insert and stripper bushing. The punch assembly provided by the manufacturer is commonly referred to as a punch canister and consists of a punch head which has threads for engaging the threads of the punch insert, a retraction spring, and includes a provision for holding the spring in place. Since the punch insert and stripper set has nothing for adjusting the punch recess, the entire mechanism for controlling the punch lead or recess must be contained in the punch canister assembly. While the invention is particularly well adapted for use in a canister punch assembly of the kind described, it can be practiced in a variety of punch sets of different types. A preferred embodiment that is described and shown in the Figures illustrates but one of the various ways that the invention can be practiced within the scope of the appended claims.
Various punch assembly adjustment devices previously proposed are described in U.S. Pat. Nos. 6,895,797; 5,647,256; 5,329,835; and 4,375,774. In some cases the recess adjustment of the punch is contained on or within the punch insert or is a part of the bushing which surrounds it. This, of course, is unacceptable for a canister style punch assembly since the “stock,” i.e., commercially available, punch insert and stripper bushing sets contain no recess adjustment feature. In other cases, changes in the recess or lead of the punch insert can only be made by partially or completely disassembling the punch set or by using tools to make changes in the punch lead. In the case of U.S. Pat. Nos. 5,647,256 and 6,895,797, the punch assemblies are not suited for use with a stock punch set provided by the end user but must include the punch and/or stripper supplied by the manufacturer as a part of the complete assembly. In addition, recess adjustments cannot be made with the punch insert in situ.
In view of these and other deficiencies of the prior art, it is one object of the present invention to provide a punch assembly with a self-contained device in which changes in the distance the punch is recessed within the stripper can be made manually without the use of tools.
Another object of the invention is the provision of an improved punch assembly having a recess adjustment in which the entire recess adjustment mechanism is contained within a canister style punch set can be used in conjunction with a any of a variety of standard size, i.e., “stock,” punch insert and stripper bushing sets that are kept in stock by the end user and are attached or replaced on the canister assembly as needed and including a feature for enabling the recess adjustment of the punch to be made with the punch in situ whereby the recess adjustment can be observed by the operator while being made.
Another more specific object of the invention is the provision of an improved punch assembly in which precise recess adjustments can be easily made without tools and in which the punching operation is performed by a punch insert and stripper guide bushing set that together have no adjustment feature and which can be removed together and replaced by hand without the use of tools whenever required.
These and other more detailed and specific objects of the present invention will be better understood by reference to the following figures and detailed description which illustrate by way of example but a few of the various forms of the invention within the scope of the appended claims.